1. Field of the Invention
The invention is in the field of manufacturing methods for the shaping of polymeric materials.
2. Description of the Prior Art
Devices of a class of opto-electronic devices comprise a substrate, at least one semiconductor element, which is electrically connected to the substrate, and a dome-shaped transparent member which encloses the semiconductor element. In many such devices the semiconductor elements include at least one light emitting semiconductor element, such as a diode, and at least one light responsive semiconductor device, such as a phototransistor. These opto-electronic devices are known as opto-isolators or optically coupled isolators. The light responsive semiconductor device produces an electrical signal in response to light received from the light emitting semiconductor device. The light travels from the emitter to the responsive device within the dome-shaped member. The dome-shaped member is then enclosed by an opaque material to confine the light and shield the light responsive device from ambient light.
In one prior art embodiment, the dome-shaped transparent member is composed of a polymer material, such as a silicone. In one method for the formation of such a device, the dome-shaped transparent member is formed by first preheating the substrate to a temperature of from 360 to 400 degrees Fahrenheit, then dispensing a quantity of the polymer onto the preheated substrate. This produces an immediate partial cure of the dome-shaped transparent member, before it can flow out along the substrate. In this method, the viscosity of the single polymer material, the pressure with which it is dispensed and the temperature of the preheated substrate must all be carefully controlled so as to insure that the dome-shaped transparent member retains its desired shape. If this shape is not retained, some limitations are imposed upon the functioning of some opto-isolators through reduction of the coupling efficiency within the device and producing light leakage to the ambient. It may also be desired to avoid preheating the substrate as either the substrate or some of the materials affixed to the substrate may be heat sensitive and adversely affected.